The present invention relates to a probe scanning apparatus for a scanning type probe microscope or the like and, more particularly, to a probe scanning apparatus which is enabled to scan a probe by integrating a mechanism for a z-coarse movement to bring a miniature probe close to a sample surface and for z-fine movement to control the distance between the miniature probe and the sample surface and a mechanism for x- and y-scans to scan the sample surface and which is additionally given a zooming function.
One example of the scanning type probe microscope of the prior art will be described with reference to FIG. 8. On the upper face of a cylindrical piezo element 55, there is mounted a sample bed 51. On this sample bed 51, there is placed a sample 52. Over this sample 52, there is oppositely disposed a miniature probe 54 which is carried on the free end of a cantilever 53. On the cylindrical surface of the piezo element 55, there are formed an electrode 56, which is wound around the cylindrical surface for the z-fine movement, and four quarter electrodes 57a, 57b (although not shown), 58a and 58b (although not shown) for the x- and y-scanning operations. A pulse motor 60 is given a performance of about 500 angstroms/pulse so that a screw rod 61 is turned to move the piezo element 55 coarsely in the direction z when the pulse motor 60 is activated.
The warpage of the cantilever 53 is detected by a position detector 73 in terms of a laser beam 72 outputted from a laser generator 71. The position detector 73 is composed of four quarter light detecting electrodes and is so positioned that the spot of the laser beam 72 comes to the center of the four quarter electrodes when the warpage of the cantilever 53 is 0. As a result, when a warpage occurs in the cantilever 53, the spot of the laser beam 72 moves over the four quarter electrodes so that a difference is made among the voltages outputted from the four quarter electrodes. These voltages are amplified by an amplifier 74 and inputted to a differential amplifier 75. The inverted input terminal (-) of this amplifier 74 is set with a reference value of the warpage of the cantilever so that the output of the differential amplifier 75 is 0 when the warpage is 0, for example.
The differential output of the differential amplifier 75 is inputted to an integration circuit 76 and a proportional circuit 77 so that the difference is averaged in the integration circuit 76 whereas its high-frequency component is extracted in the proportional circuit 77, The averaged difference and the high-frequency component are synthesized, and the synthesized output is then amplified by a voltage amplifier 78 until it is applied to the electrode 56. The circuit, as composed of the position detector 73, the amplifier 74, the differential amplifier 75, the integration circuit 76, the proportional circuit 77 and the voltage amplifier 78, defines a feedback circuit. A CRT 80 receives the x- and y-direction scanning signals from a raster scanner 81 and the warpage signal of the cantilever 53 from a line 82 so that it displays either the shape of the surface of the sample 52 or the physical properties on the display.
In the scanning type probe microscope of the prior art, as described above: the z-coarse movement is effected by the pulse motor 60 and the screw rod 61; the z-fine movement is effected by applying the feedback signal to the cylindrical electrode 56 on the piezo element 55; and the x- and y-scans are effected by applying the x- and y-scanning signals, as outputted from the raster scanner 81, to the four quarter electrodes 57a, 57b, 58a and 58b.
Since the prior art uses the piezo scanner having the construction described above, the relation (i.e., the applied voltage--displacement characteristics) between the voltage, as applied to the electrode of the piezo element, and the displacement of the same is non-linear, thereby causing a problem that the displacement cannot be enlarged. Moreover, a voltage as high as several hundred to one thousand volts has to be applied to the electrode. This makes it necessary to shield the periphery and to provide a protection circuit for dropping the voltage when the apparatus is opened. This raises a problem that the apparatus is difficult to handle.
Therefore, the owner of the present application developed and filed a patent application in Japan under Japanese Patent Application No. 25301/1996) and in The United States under Ser. No. 08/800,074 filed Feb. 12, 1997, now U.S. Pat. No. 5,945,671 for a sample positioning apparatus in which the pulse motors and screws for the z-coarse moving mechanism are replaced by a housing having a viscous element, a heater mechanism and a voice coil mechanism and in which the piezo element for the z-fine moving element is replaced by a spring element.
According to this sample positioning apparatus, all of the foregoing problems, associated with the piezo scanner can be solved, and what is provided is an apparatus in which the z-coarse mechanism and the z-fine mechanism are integrated. However, the apparatus has failed to take consideration the integration of those mechanisms with an x-y scanning mechanism. Nor any consideration is taken into the provision of a zooming function.
An object of the present invention is to eliminate the above-specified problems of the prior art and to provide a probe scanning apparatus of simple construction, in which z-direction coarse/fine mechanisms and x- and y-scanning mechanisms are integrated and which is provided with a zooming function.